Typically, a TPV is formed by a process known as dynamic vulcanization, wherein the elastomer and the thermoplastic matrix are mixed and the elastomer is cured with the aid of a crosslinking agent and/or catalyst during the mixing process. A number of such TPVs are known in the art, including some wherein the crosslinked elastomeric component can be a silicone polymer while the thermoplastic component is an organic, non-silicone polymer (i.e., a thermoplastic silicone vulcanizate or TPSiV).
U.S. Pat. No. 6,759,487 describes a re-processable thermoplastic composition comprising a thermoplastic polyurethane polymer and a silicone elastomer in weight ratio 95:5 to 15:85. The silicone elastomer is the reaction product of dynamic vulcanisation of a diorganopolysiloxane gum, a reinforcing filler, an organohydrido silicon compound and a hydrosilation catalyst. We have found that such limits do not permit to achieve a thermoplastic elastomer composition able to form a wearable item intended to be in contact with the wearer's skin when in use. As a consequence, the present invention describes a narrower range of formulation (A) over (B) able to provide superior scratch, abrasion resistance and chemical resistance. Moreover, the present invention highlight needs of specific selection of base polymer (A).
U.S. Pat. No. 6,153,691 describes preparing a thermoplastic elastomer by mixing a thermoplastic resin, a silanol-terminated diorganopolysiloxane, an organohydrido silicon compound and a condensation catalyst, and dynamically curing the diorganopolysiloxane. EP 2380 933 describes preparing a thermoplastic elastomer by side injection of 2 parts liquid silicone pre-polymer, one part comprising a catalyst and the other part SiH crosslinker to achieve silicone cure. Preparation method described in the present invention is based on use of a 3 separate silicone products: a silicone base (B1), an organohydrido silicone (B2) and a hydrosilylation catalyst (C).
We have found according to the invention that certain thermoplastic compositions comprising a thermoplastic urethane polymer and a silicone elastomer, having particular ratios of silicone to urethane polymer and of reinforcing filler to silicone, have a desirable soft touch feel to skin, and good scratch resistance and chemical resistance when used in prolonged contact with human skin.